The present invention relates, in general, to materials handling equipment and, in particular, to a pump feeder of materials handling equipment that feeds bulk materials.
In certain bulk materials handling equipment, such as the equipment described and illustrated in U.S. Pat. Nos. 5,051,041 and 5,355,993, a pump feeder moves bulk material through a housing from an inlet to an outlet by a rotating drive rotor having two or more drive discs mounted to or integral with a rotating hub. In the past, this type of equipment has been used for feeding coal and other breakable material having uniform and non-uniform gradation. Typically, the drive systems for this equipment have delivered large torque at slow speed.
As such equipment is adapted to handle different materials supplied in different sizes, problems that have not been encountered previously are arising. One such problem of major importance is the tendency of smaller size equipment, handling harder, smaller size material such as plastic, to stall, sometimes only temporarily, as the material being handled wedges between the rotating drive rotor and the housing or stationary parts mounted to the housing. This wedging of material can occur, for example, between the drive discs of the drive rotor and the housing inner wall or between the hub of the drive rotor and a materials scraper mounted to the inner wall of the housing.
Simply increasing the drive power (i.e., providing a larger drive motor) to overcome the wedging is not, in most instances, an adequate or satisfactory solution to the problem. Cost and space limitations are but two restrictions on simply providing increased drive power. Certain of the materials being handled are not easily breakable, so a larger drive motor simply increases the effect of the material wedging between the rotating drive rotor and the housing or stationary parts mounted to the housing. This can result in a complete stoppage of operation and damage to the equipment. With breakable materials, such coal, the drive torque is large enough to break or pulverize the material into smaller pieces that do not wedge between the rotating drive rotor and the housing or stationary parts mounted to the housing.
Although this adverse wedging effect might not be a regular occurrence and is likely to be different for handling different types of material, when it does occur, even temporarily, it affects accuracy and feeder performance to an unacceptable extent. Because the tendency of the equipment to stall, either temporarily or for longer periods of time, due to this wedging is greater at higher speed operation of the equipment, slowing down the operation of the equipment to reduce the likelihood of material wedging, while possibly reducing the likelihood of wedging, also is unacceptable.
A bulk materials pump feeder, constructed in accordance with the present invention, includes a housing having an inlet, an outlet, and an inner wall extending from the inlet of the housing to the outlet of the housing. This bulk materials pump feeder also includes a drive rotor having a hub rotatable about a rotation axis and a plurality of drive discs extending away from the hub toward the inner wall of the housing. The distance between the circumferential edges of the drive discs and the inner wall of the housing increases from the inlet of the housing to the outlet of the housing in the direction of rotation of the drive rotor. The inner wall of the housing, the drive discs, and the hub define a materials transfer duct through which material is transferred from the inlet of the housing to the outlet of the housing.